Expose TcpRepairWindow as module-lib API

Connectivity service is going to become a mainline module which
will not be able to access hidden APIs. TcpKeepaliveController
is a part of CS mainline module, it uses TcpRepairWindow to
store tcp repair window info. Thus, expose TcpRepairWindow as
module-lib API to support the usage.

Bug: 172183305
Test: atest FrameworksNetTests
Change-Id: I1b6f5ae698f4b6e030a0f776aeafc774fa9f1437

core/java/android/net/TcpRepairWindow.java

@@ -16,12 +16,15 @@
 
 package android.net;
 
+import android.annotation.SystemApi;
+
 /**
  * Corresponds to C's {@code struct tcp_repair_window} from
  * include/uapi/linux/tcp.h
  *
  * @hide
  */
+@SystemApi(client = SystemApi.Client.MODULE_LIBRARIES)
 public final class TcpRepairWindow {
     public final int sndWl1;
     public final int sndWnd;